Medium effects on high $p_{\rm T}$ particle production measured with the PHENIX experiment

Abstract

Transverse momentum (\(p_{\rm T}\)) spectra measured by the PHENIX experiment at RHIC in Au + Au, d + Au and pp collisions at \(\sqrt{s_{\mathrm{NN}}} = 200 \mathrm{GeV}\) and in Au + Au collisions at \(\sqrt{s_{\mathrm{NN}}} = 62.4 \mathrm{GeV}\) are presented. A suppression of the yield of high \(p_{\rm T}\) hadrons in central Au + Au collisions by a factor 4-5 at \( p_{{\text{T}}} > 5 \) is found relative to the pp reference scaled by the nuclear overlap function \(\langle T_\mathrm{AB} \rangle\). In contrast, direct photons are not suppressed in central Au + Au collisions and no suppression of high \(p_{\rm T}\) particles can be seen in d + Au collisions. This leads to the conclusion that the dense medium formed in central Au + Au collisions is responsible for the suppression.